Rolf Mowatt-Larssen is now a senior fellow at the Belfer Center at Harvard University's Kennedy School of Government.

Ann Hermes/The Christian Science Monitor

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Rich Clabaugh/Staff

Rich Clabaugh/Staff

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BOSTON — Like many terrorism experts at the time, Rolf Mowatt-Larssen wasn't taking Osama bin Laden too seriously when he said he wanted to obtain a nuclear bomb. Then he heard about "the meeting."

Mr. Mowatt-Larssen was working as the Central Intelligence Agency's top counterterrorism expert on weapons of mass destruction (WMD) – a post CIA director George Tenet had appointed him to after 9/11 since the US knew so little about Al Qaeda's capabilities. [Editor's note: The original version misspelled George Tenet's name.] The agency found out that in August 2001 – even before the World Trade Center attacks – Mr. bin Laden and one of his lieutenants had met in Afghanistan with Sultan Bashiruddin Mahmood, a gas-centrifuge expert in Pakistan's nuclear weapons program.

"For me, the galvanizing moment was probably when I found out that Mahmood ... was sitting around a campfire with bin Laden describing how to build a nuclear bomb," Mowatt-Larssen says. "I realized ... we're dealing with something we hadn't even been contemplating was possible" – a systematic plan by a terrorist to build a nuclear weapon.

Since then, Mowatt-Larssen has spent most of his days in various roles – including four years as the CIA's top WMD sleuth – trying to follow the terrorist trail and prevent rogue elements from acquiring weapons of mass destruction.

Today the former CIA agent who spent most of his nearly three-decade career in the shadows is speaking out more freely from his perch in academia about the looming terrorist nuclear threat. His overarching conclusion: The US is behind in the cat-and-mouse game to keep nuclear materials out of the reach of terrorists. While he doesn't think a nuclear attack on US soil is inevitable, neither does he find it impossible. Far from it.

More than anything, he thinks the international community needs to cooperate more to prevent bomb-grade uranium and plutonium, increasingly available on the black market, from falling into terrorists' hands. He is even promoting the controversial idea of establishing a clandestine group to acquire weapons-grade material and smuggle it into the US, as a way to goad the country into taking the threat seriously.

"I've got a conviction that the terrorists are ahead of us on this and that we've got to close the gap," says the veteran intelligence officer. "Not so much on their capability of producing a nuclear weapon, but their intent – certainly their intent is strong."

MOWATT-LARSSEN IS SOMETHING of a Renaissance man in spy clothing. He speaks four languages, including fluent Russian, and is a skilled pianist and former paratrooper. He's tall, with a shock of white hair. His office at Harvard University is spare. [Editor's note: The original version said Mowatt-Larssen teaches at Harvard. He is a scholar there.] Photographs of his wife and three children grace his desk, while books on subjects ranging from the history of nuclear intelligence to physics for the lay person jostle for space on shelves with stacks of personal notebooks on WMD.

Mowatt-Larssen is careful as he speaks, as befits a career CIA officer. He admits at one point not wanting to reveal classified information. But he's also passionate about his subject, eager to detail the threat the US faces and suggest ways to deal with it.

After years spent gleaning Al Qaeda's intent and capabilities from captured computer hard drives, documents from Afghanistan, and other sources, he now believes Al Qaeda will stop at nothing to get the bomb or the materials to make one. Others agree.

"Al-Qaeda operatives have made repeated attempts to buy nuclear material for a nuclear bomb" and recruit experts, according to "Securing the Bomb, 2008," a report by Matthew Bunn, who, like Mowatt-Larssen, is a scholar at Harvard's Belfer Center. Bin Laden has called acquiring a nuclear bomb and other WMD a "religious duty" and has even gotten a fatwa to sanction it, Mowatt-Larssen says.

Acquiring a complete nuclear weapon from an unstable Pakistan or rogue nation like North Korea remains a possibility. But far more threatening, experts say, is terrorists stealing nuclear bomb material, or buying it on the black market.

For a terrorist, acquiring highly- enriched uranium (HEU) or plutonium is the critical issue: It takes less than 20 pounds of plutonium or 40 pounds of highly-enriched uranium to build a weapon. For that reason, the US and its allies are racing to put vulnerable nuclear fuel around the world under tighter security. Since 1993, the International Atomic Energy Agency (IAEA), the United Nation's nuclear watchdog, has identified more than 1,300 cases of nuclear smuggling.

Still, just 18 of those overall incidents involved "special nuclear materials" that could be made into bombs – and that amounted to less than 11 pounds of weapons-grade uranium and 1 pound of plutonium. But to Mowatt-Larssen this still represents an unacceptable potential catastrophe.

"As long as we keep finding nuclear materials on the black market, we're failing," he says. "With most things, you can afford to be only partly successful. But with this, it's got to be a 100 percent success rate."

Mowatt-Larssen began to think about the problem deeply after 2005, when he transferred from the CIA to the US Department of Energy. There he organized a 600-person DOE office of intelligence and counterintelligence. At the same time, he coordinated government-wide efforts to prevent a nuclear terror attack.

Last fall, exhausted by years of being one of the main people looking through the keyhole, Mowatt-Larssen decided it was time to think about the issue in a more academic environment. In December, former Secretary of Energy Samuel Bodman praised Mowatt-Larssen's leadership at DOE, saying it had "opened new relationships with foreign partners." But Mowatt-Larssen is far from satisfied. He laments the lack of cooperation by intelligence agencies around the world. Without such coordination, he says, it all devolves into a game of spy-versus-spy.

"We have a collective obligation to go out there and identify what's there and bring it back to some form of control, so that terrorists can't get their hands on it," he says. "If there's no material, there there's no possibility of a bomb ever going off."

Like many, Mowatt-Larssen was heartened by President Obama's recent speech in Prague pledging to redouble efforts to clamp down on the international black market for nuclear bombmaking materials. Obama's DOE has requested $2.1 billion for nuclear nonproliferation efforts, a 44 percent increase.

But he remains skeptical whether US agencies and other nations will follow through and implement a top-priority nuclear policy. The world "is even further behind the US," he says. "Many of our allies haven't yet come to the place where they think it's a serious problem."

TO CONVINCE EVERYONE how serious it is, Mowatt-Larssen has come up with a controversial idea – the "Armageddon test." "If an intelligence officer and his team can go out there and collect enough material themselves to make a bomb, then we know we've got a problem, don't we?" he says. "So let's go find out whether that's possible."

He proposes more than just sending a team of operatives to acquire nuclear fuel on the black market: He wants them to smuggle the material back into the US to show that terrorists could do this.

Some experts endorse the idea of closer international ties and more intense black-market investigation. But the suggestion of spiriting nuclear material into a major US city is anathema to many others, who feel it would do little to improve US security and probably harm it by diverting valuable resources from efforts to secure stockpiles.

Mowatt-Larssen now says that sneaking the material into the US, while useful, may not be essential. "I don't think I would necessarily go as far as the fully developed idea of bringing [captured nuclear material] back into this country or not," he says. But then he quickly adds that it would be "a nice way" for everyone to see the full threat.

From his aerie at Harvard, Mowatt-Larssen is developing part of his idea – building a global community of intelligence analysts to work on the black-market problem. In particular, he wants to see the IAEA create its own intelligence arm so it can be a vehicle for international cooperation.

"If you look at the entire problem of nuclear terrorism as a stream – at the source there's the US, Russia, and others trying to secure materials more effectively," he says. But some material will "spill from that source and move down the stream."

The key, he says, is to have a layered defense to deal with what leaks out. That means international teams attacking the black market together and radiation sensors at borders and other last-ditch measures.

"Much has been done and security is generally improving worldwide," especially in Russia, he says. "By any normal calculus, the world is doing pretty well, and we are doing better."

"[But] I'm expecting perfection. I'm expecting never to see the terrorist mushroom cloud."